Traditionally, critical electrical systems are required to be protected against over voltages caused by faults in such electrical systems. These faults can generate much higher than normal currents and voltages across critical devices and can exceed their safe limit. For example, power systems, which correspond to an example of critical infrastructure, can experience ground faults, which result in high voltage signals being grounded, causing a current spike through equipment, and often causing damage to critical electrical equipment.
Systems have historically been developed that protect such systems during fault events. For example, in some cases, a spark gap was historically used to allow relief of overvoltage events, by allowing for a spark to form across an open air gap or in a non-combustible gas within a container to cause relief of voltage events that exceed a predetermined threshold. However, spark gaps are highly variable, and the voltage that causes such a spark to occur can vary by up to 10%-15% based on humidity and condensation or other environmental conditions. Furthermore, the total amount of energy that can be dispersed via the spark gap before the gap electrode material is destroyed by the energy of the electrical arc.
In more recent protection systems, surge arresters have been placed in parallel with power line transformers to protect during lightning strikes, ground faults, or other voltage and/or current spike conditions. In such circumstances, surge arresters provide voltage clipping at a first threshold, in which overvoltage events can be routed to ground without damaging electrical systems positioned in parallel with such surge arresters. The surge arresters have a limit to the amount of energy they can shunt to ground. If the event continues after that energy limit is exceeded, the surge arrester enters a pressure relief mode. In this event, the surge arrester is designed to safely carry the current to ground and to limit the voltage on the protected system (e.g. as described in IEEE C62.11) but is unusable afterwards.
Accordingly, the various systems and methods that have been used experience disadvantages in operation that render them, at times, to be suboptimal for reliable protection for electrical systems.